I was recently the victim of a spoiler. It was the day after the two-hour finale of Downton Abbey, and I hadn't watched it yet. I innocently went on Facebook for my daily dose of family vacation and gourmet dinner photos, and there it was: a major plot twist divulged, courtesy of one of my "friends."

My tale of woe will likely sound familiar to many. The combination of social media, which allow us to react to events in real time, and new technologies, which provide us with countless ways to watch shows after they air, has made it easy to accidentally learn how a TV episode or movie ends before watching it. It isn't surprising, then, that the spoiler issue has been chewed over for years. Way back in 2008, on New York's Vulture site, Dan Kois even proposed a list of statutes of limitations for spoilers, specifying how long writers should wait before revealing important plot twists from TV shows, movies, plays, and books in their articles.

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But this most recent spoiling left me feeling especially outraged—which, in turn, led me to wonder: Why did I care? Why were spoilers so bad? It turns out, I found, there's scientific research that helps explains what it is that spoilers spoil.

Some of this research starts with a fundamental question: Why do people like stories in the first place? As Yale psychology professor Paul Bloom points out in his book How Pleasure Works, it's puzzling that we spend more of our free time exploring fictional worlds—reading, watching TV and movies, playing video games—than engaging in real-world pastimes. "Surely we would be better off pursuing more adaptive activities—eating and drinking and fornicating, establishing relationships, building shelter, and teaching our children," he writes.

So what's with our obsession with make-believe? Bloom and others argue that, on some level, we don't distinguish fact from fiction. There's research to back this up: For example, a study found that people refuse to eat a piece of fudge shaped to look like feces, even though they know it's just fudge. Appearance and reality get blurred. We like stories about sex because we like having sex, and somewhere in our minds, the two are the same. As Thalia Goldstein, a psychology professor at Pace University, explained to me, this blurring actually happens at the neurological level: The conscious, thinking parts of our brain tell us that a story isn't real, but the more primitive parts tell us it is.

This research suggests one explanation for why spoilers suck: They remind us that a story is just a story. It's hard to get transported when you already know where you'll end up—in real life you don't have that knowledge.

Of course, not everyone shares my spoiler hatred. A recent study found that people who heard the "spoiled" version of a short story liked it more than those who heard the "unspoiled" version. But as Goldstein pointed out, the study overlooked a key fact: People only care about spoilers for stories they feel invested in, not those they've heard for the first time a minute earlier.

Spoilers suck because they remind us that a story is just a story. It's hard to get transported when you already know where you'll end up—in real life, you don't have that knowledge.

Some spoiler defenders make more theoretical arguments, such as Time's TV critic James Poniewozik, who wrote, "An unwanted spoiler does take something away, but not, I think, the pleasure of actually reading or watching a story. Rather, it takes away from the anticipation before watching it—wondering who dies, whether they'll get off the Island."

But taking away the anticipation does take away the pleasure of a story. There's plenty of research showing that people enjoy the anticipation of something pleasurable as much as—or sometimes even more than—they enjoy the thing itself. That's why a study found that people would rather postpone a free dinner at a French restaurant by a week than have it right away; they want the pleasure of looking forward to the meal. As Harvard psychology professor Daniel Gilbert says in his book Stumbling on Happiness, "Forestalling pleasure is an inventive technique for getting double the juice from half the fruit."

Others point out that if knowing major plot twists inevitably spoiled stories, people wouldn't enjoy reading the same book or watching the same movie over and over, and wouldn't flock to see movies like Argo, for which most people already know the ending. But watching a favorite movie for the hundredth time affords a kind of pleasure that is very different from—and, I would argue, not as strong as—what you experience when you see it for the first time. Once you know how a story ends, you can no longer have your mind blown; the pleasure is now in the details. Ditto for movies for which you know the ending before they even start. As Goldstein noted, "Nobody goes to a James Bond movie wondering if the crime is going to get solved and justice served—you go to see explosions and whatever the women are wearing or not wearing." Maybe that's one reason most romantic comedies are so bad, as Christopher Orr argued recently in The Atlantic—you already know how things end, and the details aren't very interesting.

What about people who read spoilers intentionally? You know these people (or perhaps you're even one of them): They claim that spoilers free them from the anxiety of watching or reading something suspenseful. Maybe they just don't know what's good for them. Or maybe, for some people, anticipation is agony; hence the expression, "The anticipation is killing me." After all, not everyone in the French restaurant study chose to put off the meal; some wanted to have it sooner rather than later.

In the end, it's hard to know how much spoilers really matter—you can't watch the same movie spoiled and unspoiled and compare your experience of each. Goldstein suggested a clever experiment that gets close: Take a group of people and have them watch two movies that include major plot twists. Half the group watches movie A spoiled and movie B unspoiled, and vice versa for the other half. Then compare people's enjoyment of the spoiled and unspoiled movies.

Until someone does that study, I'm going to stick to my spoilers-are-evil stance and try a little harder to stay out of their way. That probably means I need to avoid social media whenever there's something on the DVR. Either that or suck it up and watch my beloved shows live.